Abstract
Coupling is a critical issue for most plasmonic nanostructures. However, the coupling efficiency for many nanoplasmonic architectures is relatively weak due to the lack of theoretical optimization approaches. Consequently, it is essential to address the understanding of the mechanism and improvement of the coupling efficiency through nanoplasmonic structures. In this letter, we provide a theoretical analysis to quantitatively predict the coupling efficiency from infinite-length and finite-length nanoslits to planar metal-insulator-metal (MIM) waveguide structures, both analytically and numerically. This design principle will be useful for the development of MIM plasmonic networks to bridge the gap between photonics, optoelectronics, and nanoelectronics. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4754137]